best way i've found and use is to beg/borrow/steal.. and last resort, rent an ADAT machine... from your board use the insert jacks to the adat, only push the plugs in to the first 'click', not all the way, then it dosn't interupt the signal to the board. Do this for each channel of vocals/instrumentals... this then gives you the 'raw' signal from each input which you then can take home and 'mix' to the proper levels at your lesure. YOu could even point mics at the audience and record levels there to mix into the main sound at a later date. (just make sure those mics arn't going into the main mix for the audience... )
hope this makes sense.... works great.. i've done it for several gigs with our band.. and like the effects.. i can then download the whole thing to the computer and edit on the computer... then you're not worried about getting the 'perfect' mix during the live gig to get the best sound for the taping...

musicman